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Gross anatomy

The male urethra measures, on average, 18-20 cm in length. It commences at the internal urethral orifice in the trigone of the bladder and opens in the navicular fossa of the glans penis at the external urethral meatus, which is the narrowest part of the urethra.

The male urethra can be divided into anterior and posterior portions. The anterior urethra is composed of the penile and bulbar urethra to the level of the urogenital diaphragm. The posterior urethra is composed of the membranous and prostatic urethra.

Variant anatomy

Radiographic features

Fluoroscopy

The division into anterior and posterior urethras is important in terms of pathology and in imaging the urethra: the anterior urethra being visualised by performing a retrograde (ascending) urethrogram and the posterior urethra with an antegrade (descending or micturating) urethrogram.

MRI

sagittal and coronal images may show the course of the anterior and posterior urethra but often the proximal prostatic and penile urethra are not well seen unless there is an in-dwelling (Foley) catheter